The proposed project is a combined anatomical, physiological and histochemical study of the development and plasticity of two columnar systems in the visual cortex. A new method, 2-deoxyglucose autoradiography, will be applied to follow the normal development and plasticity of the system of orientation columns in the cat's primary visual cortex (area 17) with the aim of determining whether visual experience guides the development of the connections underlying orientation selectivity or whether it merely maintains the responsiveness and selectivity of cells whose pattern of connections is established innately. Parallel physiological and histochemical experiments on the secondary visual cortex (area 18) will examine the generality of conclusions drawn from the primary area. Ocular dominance columns in area 17 develop postnatally by a progressive segregation of the geniculocortical afferents in layer IV. To determine how afferent activity influences this segregation, I will pharmacologically block all spike activity in both optic nerves, and then stimulate electrically to restore it in defined patterns. Effects on the formation of the ocular dominance columns will be assayed both anatomically and physiologically. The objective of the proposed research is to understand the role of afferent neuronal activity in the development of the mammalian visual cortex.